Parentesco e investimento cerebral em espécies sociais de Hymenoptera

Abstract

The social brain hypothesis holds that individuals living in stable social groups face a series of challenges, such as internal conflicts, that solitary organisms do not experience, so that sociality imposes a pressure for cognitive ability. An alternative hypothesis called "distributed cognition hypothesis" predicts a negative correlation between sociality and brain size in social insects: since there is a high degree of within-group relatedness between workers, and consequently a predominance of altruistic behaviours, to the detriment of cognitively challenging internal conflicts, the demand for brain investment is lower. The relationship between kin structure and brain investment in social Hymenopteran species was evaluated here. After compiling data available in the literature, a comparative analysis was performed using the independent phylogenetic contrasts method. Brain investment was measured as the relative size of the mushroom bodies, areas of the insect brain involved with cognitive processes. The results indicate that, as proposed by the distributed cognition hypothesis, within-group relatedness is negatively associated with brain investment. Similarly, the mean number of queens per colony, a measure that is linked to decreased relatedness between workers, showed a tendency to be positively correlated to mushroom bodies volume. The queen(s) effective mating frequency, however, a phenomenon that also implies in a decrease of kinship, was not related to brain investment. Therefore, our work indicates that structural differences in insect societies may generate a demand for greater or lesser brain investment among the social species of Hymenoptera.